Cookie Policy

What is a cookie?

A “cookie” is a file that contains small amounts of information that is downloaded on your computer -or other device- by accessing certain web pages and that gathers information regarding your browsing on the websites. Once downloaded into your device, your browser sends these cookies in subsequent visits to the websites already visited, providing them with information (such as, for example, the browser used, the language selected, the number of times you have visited the page, etc.), in order to facilitate, personalise and make the navigation more effective according to the information provided by cookies.

What type of cookie do we use?

Our website uses cookies to personalise the content and provide you with a customised, efficient browsing. We use cookies to help us to identify your browser and the language that you use, as well as other characteristics of your browsing patterns, with the aim of directing you to the suitable home page and facilitating you the navigation on our website. We use identifiers, such as IP addresses to obtain the number of individual visitors that access to our website, their geographical location, and their usage trends across the different pages that make up the site. In no case shall we use cookies to personally identify the user.

By browsing our website you accept the implementation of cookies, which you can control and administrate using the properties of your browser. Note that removing or blocking cookies may affect your browsing on our website, and it is possible that some functions may not be available and may even disable browsing.

The website uses cookies with different functionalities:

Our website cookies installed on the users’ devices are not everlasting, rather, depending on their functionality, they have a limited permanence: from those cookies that delete themselves at the end of a browsing session, to other cookies that expire after 24 hours, up to the longest lasting cookies which expire 365 days after they were last updated.

The following table displays the first-party and third-party cookies that the website current uses and the purpose for which each one is used:

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cookieaccept 365 DAYS If users have accepted the cookies Disablement of the browsing on the website
_ga 1 day This type of cookie is associated with Google Universal Analytics- which is an update of the commonly used Google analysis service. This cookie is used to distinguish unique users by assigning them a number as a client identifier. It is included in each website request and is used to calculate visits, sessions and company data for the analytical reports of the website. By defect, they expire after 2 years, but this can be modified by the website owner. Impacts of the functionality of Google Analytics
_gat   This type of cookie is associated with Google Universal Analytics. Pursuant with their documentation, they are used to speed up the ratio of requests, limiting the gathering of data on websites with lots of traffic. They expire in 10 minutes. Impacts on the functionality of Google Analytics
_gid 1 day This type of cookie is associated with Google Universal Analytics. It saves and updates a unique value for each web page visited. Impacts on the functionality of Google Analytics
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JSESSIONID At the end of the browsing session Platform session cookie with a general purpose. Used on sites written in JSP. It is normally used to maintain the users’ session anonymous for the server. Impacts on the management of users.

This website uses “Google Analytics” analysis cookies, an analytical web service provided by Google, Inc. with registered address in the United States with central headquarters at 1600 Amphitheatre Parkway, Mountain View, California 94043. For the provision of these services, cookies are used which gather the information, including the users’ IP address, which will be transmitted, processed and stored by Google in the terms established on the website, including the possible transmission of said information to third parties for legal reasons or when said third parties process the information on behalf of Google. The configuration of these cookies is predetermined by the service offered by Google, as such we recommend that you check the Google Analytics privacy page to obtain more information regarding the cookies they use and how to disable them, understanding that we are not responsible for the content or veracity of third-party websites.


Users can allow, block or remove cookies stored on their device through the browser setting options on their computer. Please read carefully the corresponding help section on your browser to learn more about how to activate the “private mode” or unblock certain cookies:

Enresa wishes to point out that the variation of cookies that this website handles cannot be related to its management and maintenance. Consequently, reviews are carried out periodically to improve and update Cookies Policy.

Enresa does not assume any liability which may arise from legal or technical problems caused due to non-compliance with the recommendations included in this policy. This communication is made for inform the users and, therefore, it should not be used for any other purpose. Likewise, responsibility for the content and veracity of the privacy policies of third parties included in this Cookies Policy is not assumed.

If you have any question regarding the Cookies Policy outlined in this document, you can contact us at


Enresa can modify this Cookies Policy pursuant to the legislative or regulatory requirements, or in order to adapt that policy according to the instructions given by the Spanish Data Protection Agency. For that reason, users are advised to check this policy regulary.

High Level Waste

High-level waste (HLW) is radioactive waste containing appreciable quantities of radioactive products (long-lived alpha emitters and beta-gamma emitters), that is highly radioactive and generates a significant amount of heat. This is essentially spent nuclear fuel (SF) from nuclear power plants and vitrified waste produced in the reprocessing of small quantities of SF.

Special waste (SW) is long-lived waste of a significant activity level, the temporary and definitive management of which will be similar to high-level waste.

Characteristics of spent fuel (SF)

Nuclear fuel comprises a set of cylindrical ceramic pellets of uranium oxide, U-238, with a degree of U-235 enrichment (less than 5%), positioned within tubes made from a zirconium-rich alloy known as Zircaloy, and assembled within a structure comprising the fuel element.

Once the fuel is loaded into the nuclear reactor, it undergoes certain reactions comprising neutron capture and nuclear fission in part of the uranium and other radionuclides generated, giving rise to fission products, activation products and the generation of plutonium and minority actinides, presenting a composition containing practically all elements of the periodic table. These reactions give off a great amount of heat.

The quantities and characteristics of the different components of the SF depend on its initial U-235 enrichment and the degree of burn-up of the fuel and how the reactor was operated. The SF composition varies over time because of nuclear reactions, disintegration processes and other nuclear reactions which take place inside, and also depends on the time that has passed since it was unloaded from the reactor (cooling time).

Infographic of a fuel element

Infographic of a fuel element

Nuclear Fuel Cycle

The nuclear fuel cycle covers every stage from the extraction of the uranium ore, its concentration, enrichment and production of fuel elements for use at the nuclear power plant where the reactor causes the fission reaction (first part of the cycle), to the management of the radioactive waste generated (second part of the cycle).

Explanation of the image:
Diagram explaining the open and closed spent fuel cycles; in the open cycle: the spent fuel is considered high-level waste and is managed as such, being stored at specific temporary facilities. The definitive disposal of spent fuel would be in a deep geological repository, constituting its final management as waste.
In the closed cycle, the spent fuel is partially reused by means of reprocessing and recycling. This comprises the recovery of those components of the used fuel that have energy potential, essentially the uranium and plutonium, to be reused in a reactor. This fuel, comprising plutonium and uranium oxides, is known as MOX.
The other components of the spent fuel (fission and activation products and other actinides, structural materials) are considered waste, and are conditioned and transported to a storage facility. As in the open cycle, their final management requires them to be housed in a deep geological repository.
Diagram explaining the open and closed spent fuel cycles

Once it has been extracted from the nuclear reactor, the spent fuel element must be stored underwater at all times, to be cooled in the pools at the nuclear power plant. The choice of water as host medium is based on its high heat transfer coefficient, its good shielding properties, transparency and manageability. Following several years of cooling, the following options are available:

Open cycle:

The SF is temporarily stored in the pools at the nuclear power plants, or in other temporary storage systems, awaiting final management in a deep geological repository (DGR).

Closed cycle:

The SF is reprocessed, to recover the uranium and plutonium it still contains and manufacture new fuel. The resulting radioactive waste is vitrified and managed as HLW in temporary storage facilities awaiting final management in a deep geological repository.

Spent fuel management

Spain has opted for the open cycle, in other words it does not reprocess the SF. Only the SF from the Vandellós I nuclear power plant, in its entirety, and small amounts from the José Cabrera and Santa María de Garoña plants, were reprocessed in the past. The vitrified waste resulting from the reprocessing of spent fuel from Vandellós I is stored in France, and must return to Spain.

The strategy included in the 7th General Plan for Radioactive Waste for the temporary management of spent fuel, high-level waste, and special waste includes the Decentralized Temporary Storage (DTS) at the sites of the nuclear power plants that generate them until their final management in a Deep Geological Repository (DGR).

Temporary storage systems

Nuclear power plant´s fuel pool

Storage underwater in nuclear power plant pools

Once the SF is unloaded from the nuclear reactor, it must be stored underwater at all times in pools at the nuclear power plant, in order to cool. The choice of water as host medium is based on its high heat transfer coefficient, its good shielding properties, transparency and manageability.

Individualised Temporary Storage (ITS) facility

Dry storage in casks at the ITS facility

At some power plants the capacity of the pools is reaching its limit, or the need to evacuate fuel from the pools to begin decommissioning has been raised. In this case, the fuel is placed in casks which are stored at an appropriate facility at the power plant site. This is known as an Individualised Temporary Storage (ITS) facility.

The temporary storage casks may be of different types, such as dual-purpose metal casks (storage and transportation) or welded metal canisters stored in concrete-metal modules that can be transported in a metal cask.

Independent Spent Fuel Storage Installation (ISFSI) at the different nuclear power plants (NPP)

Trillo Independent Spent Fuel Storage Installation (ISFSI)

The Trillo nuclear power plant has since 2002 had a cask storage facility in order to temporarily hold the site's SF. This is a hall with concrete walls and roof capable of holding up to 80 dual-purpose casks (storage and transport). This ISFSI has the capacity to store all the spent fuel that is generated as a result of the operation of the plant, always in accordance with the planned closure scenario.

Trillo´s nuclear power plant ITS facility
José Cabrera ISFSI facility

Facility located on the site of the power plant and designed for the dry storage of all SF unloaded from the reactor.

It comprises a reinforced concrete slab to support the storage modules, surrounded by outer radiation protection fencing and inner security fencing to delimit the storage area.

This ISFSI facility holds 12 casks loaded with SF and a further 4 which house the more active metal parts obtained during the internal reactor component segmentation dismantling.

José Cabrera´s nuclear power plant ITS facility
Ascó Independent Spent Fuel Storage Installation (ISFSI)

Facility located within the power plant site and designed for the dry storage of SF unloaded from the two reactors.

Composed of two independent slabs for 18 storage containers each. It has a storage system based on welded metal capsules with a concrete enclosure. It is surrounded by an outer radiation protection fencing system and an inner physical security fence to delimit the storage area.

Ascó´s nuclear power plant ITS facility
Almaraz Independent Spent Fuel Storage Installation (ISFSI)

This storage facility employs similar technology to the above, based on two reinforced concrete slabs with a capacity for 20 double-purpose metal containers on its surface (10 containers on each slab). This ISFSI serves the two units of the plant.

Almaraz´s nuclear power plant ITS facility
Santa María de Garoña Independent Spent Fuel Storage Installation (ISFSI)

This ISFSI consists of 2 reinforced concrete slabs, was initially authorized for 10 containers, and the authorization for the entire spent fuel (SF) of the plant is currently being processed. The storage system consists of double-purpose metal containers.

Santa Marís de Garoña´s nuclear power plant ITS facility
Cofrentes Independent Spent Fuel Storage Installation (ISFSI)

A storage facility with similar technology to the above, based on a concrete slab with dual-purpose metal casks and capacity for two slabs and added a capacity for 12 containers each, which means a total storage capacity of 24 double-purpose metal containers.

Cofrente´s nuclear power plant ITS facility

Decentralized Temporary Storage (DTS)

The 7th General Plan for Radioactive Waste (PGRR) in Spain includes the establishment of a DTS for spent fuel, high-level waste (HLW), and especial radioactive waste (SW) at each nuclear power plant in Spain (Almaraz, Ascó, Cofrentes, Santa María de Garoña, José Cabrera, Trillo, and Vandellós II).

Each Decentralized Temporary Storage will be composed of the existing Independent Spent Fuel Storage Installation (ISFSI), plus a new complementary installation or additional measures, which will allow for the maintenance and repair of the containers, in order to guarantee the recoverability function at the container level.

The DTSs, including their complementary installations, will be operational before the decommissioning of the fuel pools. At the José Cabrera nuclear power plant, which is in the final phase of decommissioning, the measures planned for container recoverability will be implemented between 2024 and 2029.

The DTSs will remain operational until the transfer of all spent fuel to the deep geological repository (DGR).

Final storage system

In accordance with Council Directive 2011/70/Euratom of 19 July 2011, establishing a Community framework for the responsible and safe management of spent fuel and radioactive waste, the broadly accepted concept at present is that a Deep Geological Repository (DGR) represents the safest and most sustainable option as the endpoint of the management of SF and HLW.

The aim pursued by the storage of HLW in deep geological formations is to prevent the radioactive substances they contain from reaching the human environment in concentrations that could harm the natural world, and hence human health.

In order to achieve this, the waste must be isolated for lengthy time periods, allowing the level of activity of the various radioactive elements it contains to decay to sufficiently low values so as not to alter the natural background radiation, and not to increase normal doses for human beings.

The DGR is based on the so-called multi-barrier principle, which involves placing a series of artificial and natural barriers between the waste and the biosphere. Safety does not rely on one single barrier, but on the combined action of different barriers with different functions. The aim is that any deficiencies that could arise in the performance of one barrier over time would not compromise the overall safety of the system.

These barriers act in two different ways:

  • First, they serve to contain the radioactive materials
  • Furthermore, they delay and dilute potential releases into the biosphere comprising the set of ecosystems which will suffer the potential impact from the disposal facility (soil, water, living beings, etc.).

There are two types of barrier or component to this concept: artificial and natural.

Explanatory text AGP
Combination of artificial and natural barriers on a deep geological repository

Artificial barriers

Artificial barriers or engineered barriers, are designed, built and installed in accordance with the design of the disposal facility, the specific function or functions assigned to them, and the conditions imposed in the short and long term by the other artificial and natural barriers within the system.

The components of the artificial or engineered barriers are (see figure):

  • The chemical form of the waste itself.
  • The metal storage canisters.
  • The filling and sealing materials.

Natural barriers

Natural barriers are not specified or built by human hand, but must be characterised and selected in accordance with certain criteria, or functional requirements, that would allow the artificial barriers and the whole system to function properly.

The components of the natural barriers are:

  • The geosphere. Geological formations housing the repository, and the waters and gases they contain.
  • The biosphere. Set of ecosystems (soil, water, living beings, etc.) that would suffer the impact of the repository.

A geological barrier should be understood as the geological formation where the disposal facility is located, which essentially comprises a solid part, made up of rocks and minerals, and a fluid part made up of water and gases.

The natural barrier is responsible for the long-term safety of the system, delaying the emergence of radionuclides into the human environment, and controlling their dispersal and dilution. The artificial barriers play a decisive role in short-term safety, given their capacity for containment and delay.

Since 1985, Enresa has worked on the DGR option in four basic directions:

The Site Search Plan (SSP) allowed sufficient information to be gathered to ascertain that the subsoil of Spain contains plentiful granite and clay formations capable of housing a disposal facility.

Generation of conceptual designs of a disposal facility for each of the stated lithological contexts, aiming for the greatest number of points in common among all of them.

Development of Safety Assessment exercises for the conceptual designs (granite and clay), incorporating the knowledge built up during work and projects under the successive R&D Plans undertaken, highlighting that DGRs are capable of complying with the safety and quality criteria applicable to this type of facility.

Development of successive R&D plans which have gradually evolved in line with SF and HLW management plans, serving to acquire technical know-how and participate in national/international research projects at underground laboratories abroad.

Considerable research efforts have also been dedicated to the different versions of separation and transmutation technologies with the aim of reducing the level of activity and duration of the elements and facilitating their DGR storage, although the scale of such programmes necessarily requires participation at an international level.

As a result of the studies performed between 1986 and 1996, conducting an analysis of suitable geological formations to house the DGR site, an Inventory of Suitable Formations was drawn up.

Two generic designs are available, along with the safety assessment associated with both, tailored to a granite and a clay-type host medium. These advances will constitute a sound basis for the launch of the forthcoming stages for the selection of the site and the implementation of the DGR.

The reference concept assumes final storage of the SF and other HLW in carbon steel capsules surrounded by an appropriate sealant material. These capsules will be located in horizontal tunnels positioned at sufficient depth, which will vary according to whether the formations are clay- or granite-based.

The reactivation of the DGR programme in Spain, together with its regulation and a specific implementation plan, were a recommendation of the combined IRRS/ARTEMIS mission to evaluate the Spanish regulatory framework regarding nuclear and radiological safety (IRRS), and the radioactive waste management system (ARTEMIS), so as to comply with:

  • Directive 2009/71/EURATOM establishing a Community framework for the nuclear safety of nuclear installations, and
  • Directive 2011/70/Euratom of 19 July 2011 establishing a Community framework for the responsible and safe management of spent fuel and radioactive waste.

The 7th GRWP considers DGR disposal to be the preferred and basic option for the management of SF and HLW, and in terms of economic and planning calculations this would enter operation from 2073 onwards, following a prior period of temporary storage of SF.

Transport of high-level waste (HLW)

There is at present no transport of high-level waste and spent nuclear fuel in Spain, as such waste remains in the pools or interim storage facilities at the power plants themselves.

Transport container for high-level waste and spent nuclear fuel
Preparatory transport work